1. Field of Invention
This invention relates to the art of methods and apparatus for cutting elastomeric materials and especially for cutting tire components such as tire treads.
2. Description of the Related Art
In cutting an elastomeric material such as rubber with a heated knife it is important that the temperature at the heated knife blade be high enough to provide the maximum cutting speed through the material but at the same time the temperature be controlled so that the material is not cured or damaged by high temperatures during cutting. This has been a problem when cutting elastomeric material such as rubber treads of variable thickness where the heated knife is moved across the tread at a constant speed. Where the speed has been fast enough while the knife is traversing the sections of lessor thickness it has been too fast while the knife is traversing the sections of greater thickness. Accordingly the heat generated by the knife in the section of greater thickness has caused the temperature to increase to undesirable high temperatures which has caused premature curing or damage of the material.
Prior art cutters for high mass, large cross-section components of rubber material have also included conduction-heated guillotine blades to plunge cut through the rubber material. There have been problems with this type of cutter because it utilizes a wedge-shaped blade which distorts the cut surface by compressing the trailing edge and elongating the leading edge. Splice control has been difficult which adversely affects tire uniformity. This prior art system is timer driven and the cut edges are exposed to the hot knife blade as it continues to plunge through the material. In addition the hot knife is positioned above the rubber material which has caused surface blooming. By surface blooming is meant surfacing of oils due to heat. Problems have also been experienced with incomplete cutting and rebound causing the leading and trailing cut edges to adhere after being cut. Control of the blade temperature has been difficult and slow because of the large thermally conductive mass. The time required for replacement of the blades has also been substantial because the larger mass involved requires considerable time for cooling.